Method of oxidizing phosphorus



Patented Sept. 27, 1932 UNITED STATES PATENT OFFICE STAPLETON '.D. GOOCH, 01 LAKE WALES, AND WILLIAM H. WAGGAMAN, OF LAKELAND, FLORIDA, ASSIGNOBS TO CORONET PHOSPHATE COMPANY, OF NEW YORK, N. 'Y., A

CORPORATION or NEW YORK' y METHQD or 'oxrnrzrrie rnosrnomrs N0 Drawing.

This invention relates to an improved method of treating phosphorus and more particularly to a method ofv oxidizing phos phorus and producing phosphoric acid.

.Thepresent method has been devised so as to provide a-simple and economical process of procuring relatively pure phos horic acid from relatively impure phosp 'orus, without, as has heretofore been the practice, subjecting the impure phosphorus to a preliminary purification treatment. v o

The method described herein is therefore particularly applicable tothe. treatment of phosphorus containing dust or other solid impurities and is especially eflicacious in treating wet phosphorus.

A major object of the invention is to produce substantially pure, strong phosphoric acid from relatively impure phosphorus.

Another object is to treat Wet phosphorus in a novel manner so as to simultaneously efi'ect. complete oxidation of the phosphorus and humidification.

A further object is to provide a novel method of burning impure phosphorus.

With these and other important objects in view, the invention comprehends the direct and complete combustion of impure and/or wet phosphorus so as to form phosphorus pentoxide substantially free from impurities and efiectively utilize. the heat of combustion of the phosphorus to generate water vapor which provides the absorbing medium for the phosphorus pentoxide to form concentrated phosphoric acid.

The present treatment is especially, although not exclusively, adapted for use with a phosphorus sludge prepared by decomposing a phosphatic charge in a blast furnace and condensing and collecting the elemental phosphorus together with solid impurities.

The method comprises feeding such impure phosphorus by any suitable means such as by gravity, by a pump, by a drag or screw conveyor into one end of a rotary burner. The burner may be of the type used in burning sulphur for the production of sulphur dioxide in the contact process for preparing sulphuric acid. The burner may, if desired, be inclined toward the exit end to facilitate Application med April v15,

1930. Serial No.-444,606.

longitudinal movement of material. This element ispreferably lined With some acidproof and refractory material and, if desired, may be provided with vanes, baflles or other surface increasing means.

The impure phosphorus or phosphorus sludge is fed inat one end and as the burner rotates it is distributed over the inner surface. During its passage through the burner the phosphorus is exposed to a draft of air'preferably admitted at a point adjacent the feeding point'of the phosphorus. The air may be admitted under reduced or forced draft and may be controlled to any desired degree as to temperature and volume so as to regulate the 7 speed and extent of combustion. It will be observed that since the inner walls of the burner are composed of a refractory material heat .loss is largely prevented and the full thermal value of the combustion is utilized.

Byreason of thisthe inner surfaces are maintai'ned uniformly hot and hence condensation of vapors Within the burner is prevented.

In these circumstances a portion of phosphorus isburned or oxidized directly while the heat generated vaporizes or sublimes a substantial quantity of the element. It will be observed,'however, that by ,insuringa long er path of travel for the phosphorus and by controlling the temperature Within the burn- 7 er, the phosphorus may be substantially com- ,pletely oxidized within the burner.

In the preferred modification,the products of combustion are led from the rotary burner'to a separate combustion chamber where an additional quantity of air preheated to any desired degree is admitted. This treatment insures the combustion of any residual unoxidized phosphorus.

- It'will be observed that due to the thermal conditions of the operation, any water contained in the phosphorus'charge is transformed into steam and this is available to humidify the phosphorus pentoxide either inthe burner, combustion chamber or in the absorption system, In the caseof a charge of phosphorus containing fifty per ,oentor more of moisture, this water is converted to steam and on reaching :the absorbing tower orCottrell precipitator for collecting the acid,

before passing them to the absorbing units.

This may readily be done by interposing a suitable cooling means between the combustion chamber and the absorbing units. -As a typical example of a means as achieving this reduction of'temperature, acooling tower ,may be provided. In this'the gases may be introduced into the lower end and sprayed With water, so as to reduce the temperature to such a degree as will permit of ready absorption or precipitation. Obviously, however, the gases may be cooled in anyother manner. as by indirect contact with a cooling medium.

It will be observed that the process described herein provides a simple and effective method of treating impure phosphorus to prepare phosphoric acid. Any solid impurities contained in the phosphorus are left behind as a residue in the burner or combustion chamber. The heat generated by the com. bust-ion of. the phosphorus is utilized to vaporize the contained water and render it available for humidification. The method, therefore, provides, so to speak, for a simultaneous oxidation and humidification of the phosphorus, which are secured by a single treatment of one material, that is the wet phosphorus.

Therefore, while a preferred modificatlon phosphoric acid contained in the combustion gases.

3. A method of supplying water sufiici'ent for the production of phosphoric acid from phosphorus pentoxide comprising burning impure wet phosphorus sludge in a rotary burner, admitting sufiicient air for the combustion of elemental phosphorus, maintaining a temperature in the burner suiticiently high to prevent the condensation of water, withdrawing phosphorus pentoxide and water vapor and absorbing the phosphorus pentoxide in the water as phosphoric acid in anabsorption system.

4. A method fpreparing phosphorioacid comprising charging wet phosphorus having solid impurities incorporated-therewith into a rotating combustion zone in which the wet phosphorus is distributed over the inner surface thereof, admitting a combustion sup- .portlng gas into the burner, burning the wet phosphorus therein to simultaneously form phosphorus pentoxide and water vapor free from solid impurities, maintaining the temperature in the burner sufliciently high to prevent the condensation of water, then passing vapors to an auxiliary combustion zone, admitting an additional quantity of a preheated combustion supporting gas to the auxiliary combustion zone, withdrawing phosphorus pentoxi'de and water vapor from the auxiliary combustion zone and absorbingthe phosphorus pentoxide in the water as phosphoric acid in an absorption system. In testimony whereof we have aifixed signatures. p I

STAPLETON D. GOOCH. WILLIAM H. WAGGAMAN.

of the invention has been described it is to be understood that this is given merely as a typical example of the manner in which the principles involved herein may be efiectuated.

We claim; r 1. A method of producing phosphoric acid from an impure wet sludge containing elemental phosphorus comprising feeding the phosphorus sludge into one end of a rotary burner, causing combustion of the phosphorus, leading gases and vapors from the burner into an auxiliary combustion chamber and subsequently separating the phosphoric acid contained in the combustion gases.

2. A method of producing phosphoric acid from an impure wet sludge containing a mixture of yellow and red phosphorus, comprising feeding the phosphorus sludge into one end of a rotary burner, causing combustion of the phosphorus, leading gases and vapors into an auxiliary combustion chamber, and then subsequently separating the 

